The present invention relates to a method and apparatus for analyzing the state of generation of foreign particles in a semiconductor fabrication process, more particularly, detecting and analyzing foreign particles generated in a mass production starting line and a mass production line of the said process and taking an appropriate countermeasure, or a foreign particle inspecting apparatus for inspecting foreign particles on a semiconductor substrate.
In the conventional semiconductor fabrication process, if foreign particles are present on a semiconductor substrate (wafer), they will cause defects such as defective insulation of wiring and short-circuit. Further, in the case where a fine foreign particle is present in a semiconductor substrate provided with very fine semiconductor elements, such foreign particle will cause breakdown of an insulating film of a capacitor or a gate oxide film. Foreign particles are generated by various causes and in various conditions; for example, they are generated from an operating portion of a conveyance system, generated from the human body, or result from reaction in a processing apparatus using a process gas, or are already incorporated in chemicals, materials, etc.
A conventional method for detecting such foreign particles on a semiconductor substrate is disclosed in Japanese Patent Laid Open No. 89336/87, which method comprises radiating a laser beam onto the semiconductor substrate, detecting a scattered light from foreign particles if deposited on the substrate, then comparing the result with the result of inspection of the same type of a semiconductor substrate conducted just before, thereby eliminating a false information based on pattern and permitting a foreign particle inspection of high sensitivity and high reliability. Also in Japanese Patent Laid Open No. 135848/88 there is disclosed a method which comprises radiating a laser beam onto a semiconductor substrate, detecting a scattered light from foreign particles if deposited on the substrate, and then analyzing the detected foreign particles using an analyzing technique such as laser photoluminescence or secondary X-ray analysis (XMR).
In the above conventional methods, distinction is made between a mass production starting line and a mass production line in a semiconductor fabrication process, and an inspection apparatus used in the mass production starting operation is applied as it is to the mass production line, so it is necessary in the mass production line to detect the generation of foreign particles and take a countermeasure as soon as possible. However, the conventional inspection apparatus is a stand-alone type and the semiconductor substrate which has been processed in the fabrication line is carried to the installed place of the inspection apparatus and inspected there for foreign particles. Thus, it takes time for conveyance of the semiconductor substrate and for the inspection of foreign particles, so that it is difficult to increase the inspection frequency up to a sufficient value.
In the prior art, in addition to the large scale of equipment, a long time is required for the inspection, so for realizing a real-time monitor using such conventional apparatus, it is necessary to arrange a large number of large-sized apparatus, but actually this has been difficult. Actually it has been possible to inspect at most one or several lots or one sheet of a semiconductor substrate a day. In such a frequency of foreign particle inspection, it cannot be said that the generation of foreign particles is detected sufficiently rapidity. Such inspection in the prior art has been remote from the ideal real-time sampling in the mass production line. Further, for decreasing the number of steps in the mass production line and for diminishing equipment, it has been necessary to provide a required and sufficient number of monitors in a required and sufficient number of places. This has also been a subject to be attained.
One of main mass production starting operations for LSI is an operation of clearing up the cause of generation of such foreign particles and taking a countermeasure. In this connection, detecting foreign particles and analyzing the kind of element, etc. is an important clue to clear up the cause of their generation. On the other hand, in the mass production line, it is necessary to detect the generation of foreign particles and take a countermeasure as soon as possible. As time elapses from the generation of foreign particles up to the detection thereof, the number of defects generated increases and hence the yield lowers. Therefore, in order to maintain a high yield, it is absolutely necessary to shorten the time elapsed from the generation of foreign particles until the detection thereof. In other words, in order to maximize the effect of the foreign particle inspection, it is necessary to shorten the sampling time in a monitor, and ideally it is desirable to perform a real-time sampling for the mass production line.